Molecular diversity and genetic potential of new maize inbred lines across varying sowing conditions in arid environment

Abstract

Developing high-yielding and resilient maize hybrids is essential to ensure its sustainable production with the ongoing challenges of considerable shifts in global climate. This study aimed to explore genetic diversity among exotic and local maize inbred lines, evaluate their combining ability, understand the genetic mechanisms influencing ear characteristics and grain yield, and identify superior hybrids suited for timely and late sowing conditions. Seven local and exotic maize inbred lines were genotyped using SSR (Simple Sequence Repeat) markers to assess their genetic diversity. These diverse lines were utilized to develop 21 F1 hybrids using a diallel mating design. These hybrids, alongside a high-yielding commercial check (SC-10), were evaluated under field conditions across two growing seasons under timely and late sowing conditions. The results showed that sowing date, assessed hybrids, and their interaction significantly influenced all measured agronomic traits. Notably, late sowing reduced plant height, ear characteristics, and, ultimately, grain yield. Several hybrids, particularly L101 × L103, L101 × L105, L104 × L105, and L104 × L107 under timely sowing, and L101 × L105 and L104 × L107 under late sowing, surpassed the agronomic performance of check commercial hybrid. Inbred lines L101 and L103 emerged as superior combiners for ear traits and yield, while line L106 showed promise for breeding shorter-stature plants. Hybrid combinations L101 × L105, L104 × L107, and L106 × L107 were identified as specific good combiners for grain yield and related traits under both sowing conditions, indicating their potential for commercial development. Strong positive associations were observed between grain yield and certain agronomic traits highlighting their utility for indirect selection in early breeding generations.

Keywords: Climate adaptability; Combining ability; Diallel mating design; Hybrid yield performance; Plant breeding strategies; SSR markers.

Fig. 1

UPGMA dendrogram of seven parental maize inbreds based on genetic similarity from SSR markers

Fig. 2

Comparative boxplots of agronomic trait variation in F1 hybrids under timely and delayed sowing conditions. PH (plant height, cm); EH (ear height, cm); EP (ear position); EL (ear length, cm); ED (ear diameter, cm); NRE (number of rows/ear); NKR (number of kernels/row); and GY (grain yield).

Fig. 3

Comparative performance of developed 21 F1 hybrids and check hybrid (SC-10): plant height (A), ear height (B), ear position (C), and ear length (D) with Least Significant Difference (LSD) Indicators at P < 0.05 on the top of the columns.

Fig. 4

Comparative performance of developed 21 F1 hybrids and check hybrid (SC-10): Ear diameter (A), number of rows per ear (B), number of kernels per row (C), and grain yield (D) with Least Significant Difference (LSD) Indicators at P < 0.05 on the top of the columns.

Fig. 5

PCA biplot for trait variation in maize hybrids under different sowing conditions (a), bar chart detailing the percentage contribution of principal components to overall variance, and trait contribution bar charts with a dashed line demarcating significant contributions (c and d). H1 (L101×L102), H2 (L101×L103), H3 (L101×L104), H4 (L101×L105), H5 (L101×L106), H6 (L101×L107), H7 (L102×L103), H8 (L102×L104), H9 (L102×L105), H10 (L102×L106), H11 (L102×L107), H12 (L103×L104), H13 (L103×L105), H14 (L103×L106), H15 (L103×L107), H16 (L104×L105), H17 (L104×L106), H18 (L104×L107), H19 (L105×L106), H20 (L105×L107), H21 (L106×L107), H22 (SC-10). EH ear height, PH plant height, Ep ear position, ED ear diameterm, NKR number of kernels per row, EL ear length, NRE number of rows per ear, GY grain yield.

Fig. 6

Spearman correlation matrix for agronomic traits under optimal and late sowing conditions. PH plant height (cm); EH ear height (cm); Ep ear position; ED ear diameter (cm); EL ear length (cm); NKR number of kernel/row; NRE number of rows/ear; and GY grain yield. Timely sowing is marked in green while late sowing is in red colors.

Fig. 7

Heatmap of hierarchical clustering for maize hybrids based on tolerance indices. Blue indicates a high rank (less affected by late sowing), while red indicates a lower rank (more affected by late sowing). PH plant height (cm); EH ear height (cm); Ep ear position; ED ear diameter (cm); EL ear length (cm); NKR number of kernel/row; NRE number of rows/ear; and GY grain yield.

Fig. 8

Ranking of assessed maize hybrids by resilience to late sowing based on tolerance indices. Small numbers of average ranks mean less affected by late sowing (near graph bottom). H1: L101×L102, H2: L101×L103, H3: L101×L104, H4: L101×L105, H5: L101×L106, H6: L101×L107, H7: L102×L103, H8: L102×L104, H9: L102×L105, H10: L102×L106, H11: L102×L107, H12: L103×L104, H13: L103×L105, H14: L103×L106, H15: L103×L107, H16: L104×L105, H17: L104×L106, H18: L104×L107, H19:L105×L106, H20:L105×L107, H21: L106×L107, H22: SC-10.

Fig. 9

Daily minimum and maximum temperatures, alongside solar radiation levels and relative humidity across two growing seasons.